1. THE PERIODIC TABLE & IONS
CHEMISTRY N5
CHEMISTRY
ATOMIC STRUCTURE
THE PERIODIC TABLE & IONS

2. THE PERIODIC TABLE & IONS
CHEMISTRY N5
CHEMISTRY
ATOMIC STRUCTURE
THE PERIODIC TABLE & IONS
After completing this topic you should be able to :
Relate the position of an element in the periodic table to the arrangement of its electrons in the atom.
State what period and a group are in the periodic table.
State that an ion is an atom which has a charge.
State that an ion can be made from an atom by losing or gaining one or more electrons.
Work out the number of protons, electrons and neutrons in an ion, given the mass number, atomic number and charge on an ion.

3. THE PERIODIC TABLE & IONS
The rows of the Periodic Table are called the PERIODS.
The periods relate to the filling up of the energy levels with electrons.
1st energy level holds 2 electrons.
1st energy level full.
2nd energy level holds 8 electrons.
2nd energy level full.
There are 7 energy levels in an atom and there are 7 periods (rows). The energy levels further out from the nucleus can hold increasing numbers of electrons.
The numbered columns are called GROUPS.

4. ATOMS JOINING
Atoms use their outer electrons to join. It is the outer electrons on an atom which gives the atom its chemical properties.
One way atoms can join is to TRANSFER one or more electron(s) from one atom to another.
When an electron transfers from one atom to another the atoms will no longer be electrically neutral.
Charged atoms are called IONS.

5. Atoms have equal numbers of positive charges (protons) in the nucleus and negative electrons.
Atoms are NEUTRAL.
When an atom loses an electron it becomes a positively charged ion.
When an atom gains an electron it becomes a negatively charged ion.
Charged atoms are called ions.
Opposite electrical charges attract.
The ions attract each other and stick together.

6. Li+ Li O2- O ION SYMBOLS Lithium atom Lithium ion
Lithium ion has a 1 positive charge. Its atom lost 1 electron.
Oxygen atom
Oxide ion O
O2-
Negative ions end their name in ide.
Oxide ion has a 2 negative charge. The oxygen atom gained 2 electrons.

7. Al3+ Al Cl- Cl Aluminium atom Aluminium ion
Aluminium ion has a 3 positive charge. Its atom lost 3 electrons.
Chlorine atom
Chloride ion Cl
Cl-
Negative ions end their name in IDE.
Chloride ion has a 1 negative charge. The chlorine atom gained 1 electron.

8. Be2+ + + + + 9 4 + + + + IONS SYMBOL AGAIN! Protons 4 Neutrons 5
Mass Number
Atom has lost 2 electrons
Atomic Number + + + +
Protons 4
Neutrons 5
Electrons 2
Electron Arr. 2,

9. O2- + + + + + + + + 15 8 + + + + + + + + Protons 8 Neutrons 7
Mass Number
Atom has gained 2 electrons
Atomic Number + + + + + + + +
Protons 8
Neutrons 7
Electrons 10
Electron Arr.
2, 8